a) Field of the invention
The present invention relates to a microscope and more specifically a turret condenser for microscopes.
b) Description of the prior art
A condenser for microscopes must generally be designed so as to meet requirements: 1) to be compatible with various objective lenses having magnifications different from one another and 2) to be useable for microscopy in various modes using a phase plate, a dark field plate, a Nomarski prism and a polarizing plate.
In order to meet the above-mentioned requirement 1), it is necessary to adopt a mechanism capable of varying size of illumination field and numerical aperture in conjunction with objective lenses to be used for microscopy as exemplified in the condenser for microscopes disclosed by Japanese Patent Preliminary Publication No. Sho 61-34126. This condenser comprises a fixed lens and two movable lenses, and is so adapted as to be compatible with objective lenses having a broad range of magnifications by using the lenses in various combinations. The condenser for microscopes is composed, needless to say, so as to exchangeably accommodate optical elements such as a Nomarski prism, a phase plate and a dark field plate. Further, there are known, as condensers for microscopes which meet the requirement 1) and are disclosed by, for example, Japanese Patent Preliminary Publication No. Sho 49-84262, double-stage turret type condensers which comprise completed condenser lenses for high and low magnifications in a first-stage turret, and various types of optical elements such as those mentioned above in a second-stage turret.
In order to meet the requirement 2) described above, it is necessary to adopt a mechanism which permits interposing optical elements in conjunction with modes of microscopy at a location in the vicinity of the pupil of a condenser lens, and a condenser having such a mechanism is developed as a commercial product available as a universal condenser. FIG. 1 shows a single-stage type turret condenser having the general or conventional construction which permits interposing a phase plate, a dark field plate, a Nomarski prism and a stop selectively at the location of the pupil of a fixed condenser lens. In this drawing, the reference numeral 1 represents a condenser body having a mounting portion 1a, the reference numeral 2 designates a condenser lens fixed to the condenser body 1, the reference numeral 3 denotes a turret which is pivoted to the condenser body 1, and capable of selectively interposing optical elements 4 such as a phase plate, a dark field plate, a Nomarski prism and a stop which are fixed or exchangeably accommodated therein at the location of the pupil on the optical axis of the condenser lens 2, and the reference numeral 5 represents a slider which is slidably fitted in the condenser body 1 and capable of interposing an empty hole and a rotatably fitted polarizer 5a selectively on the optical axis of the condenser lens 2. The empty hole of the slider 5 is interposed in the optical path when the optical element 4 is selected so as to be suited for bright field microscopy, dark field microscopy or phase difference misroscopy by adequately operating the turret 3 and the slider 5, whereas the polarizer 5a is inserted into the optical path when the optical element 4 is selected so as to be suited for polarizing microscopy or differential interference microscopy.
The condenser for microscopes disclosed in Japanese Patent Preliminary Publication No. Sho 61-34126 has a single-stage turret, and therefore poses problems that certain accommodating holes contain no stops when Nomarski prisms are set in all of the accommodating holes for optical elements, and that a single condenser is insufficient for microscopy requiring two optical elements such as the differential interference microscopy by using a Nomarski prism and a polarizer, the polarizing microscopy by using a polarizer and a green filter, and the transmission fluorescence microscopy by using an exciting filter and a dark field plate. Further, the condenser disclosed in Japanese Patent Preliminary Publication No. Sho 49-84262 mentioned above which accommodates completed condenser lenses poses problems that the condenser requires a rather large number of lenses, and that the condenser is not only large and expensive but also it cannot accommodate numerous types of optical elements. Further, this condenser requires a large space to be reserved between the mounting portion and the condenser lens, thereby posing further problems that it constitutes a hindrance to compact design of a microscope as a whole and that it does not permit using a combination of two optical elements as described above. Furthermore, the condenser illustrated in FIG. 1 is usable for microscopy in the general modes, but the turret 3 has a limited number of accommodating holes for optical elements, thereby limiting modes of microscopy to be performed with the condenser.